The death of an East Valley man this month of West Nile virus marks the first of the season and the fourth reported case in Maricopa County this year, the county Department of Public Health announced Thursday.

The victim was in his late 60s and had underlying health issues, but public health officials urged all county residents to take precautions to prevent the mosquito-borne illness.

"No matter how healthy you are or how old you are, avoid those mosquito bites and avoid standing water in your yard," said Rebecca Sunenshine, medical director for disease control at the health department.

The West Nile virus was first detected in the United States in 1999 after migratory birds carried the disease over from the east. Arizona was among the last states to discover the virus in 2003, but it remains one of the only states to still see the disease. The Department of Public Health recorded more than 50 cases and six related deaths in 2013, but there were likely hundreds more, Sunenshine said. Only 20percent of those infected show symptoms.

"For every one that's reported, there are hundreds more out there," Sunenshine said.

The virus causes flu-like symptoms, including fever, headache and muscle weakness. More-severe symptoms include neck stiffness and inflammation of the brain.

"There is no specific treatment," Sunenshine said. "That's why we focus so much on preventing the disease."

West Nile virus is most prevalent during Arizona's monsoon and is best prevented by avoiding mosquito bites. Mosquitoes breed in standing water, which can be found in ponds, tires, dog bowls and unclean pools.

To avoid getting bit by the virus-carrying breed, people should avoid going outside at dawn and dusk and wear insect repellent and long sleeves when they do, Sunenshine said.

"There's something about Arizona that keeps it going here year after year," she said.

Mosquito complaints have been down so far this year, but that could change at any time, said Johnny Dilone, a spokesman for the county Environmental Services Department.

The county deploys hundreds of mosquito traps each week and have had 39 mosquito samples test positive for the virus.

"This is something we can all prevent by eliminating standing water," Dilone said.

For more on West Nile virus, to obtain free mosquito-eating fish, to report green pools or to file a mosquito-related complaint, call the West Nile Virus General Information and Help Line at (602) 506-0700 or visit

Wear lightweight clothing that covers your arms and legs and use an insect repellent if you must be outdoors when mosquitoes are active. Always follow the directions on the label. Getty Images/iStockphoto